One of the Con Ed workers pulled from the floodwater, Angelo Amato, told Reuters he was part of a crew who had offered to work through the storm.

"This is what happens when you volunteer."

3:07pm: On Twitter, New Jersey's governor Chris Christie says he might have to cancel Halloween.

"If conditions are not safe on Wednesday for Trick or Treating, I will sign an Executive Order rescheduling #Halloween."

3:05pm: Former ABC journalist Sarah Caddick says memories of Irene led many New Yorkers to stay put during Hurricane Sandy. Here's her story from earlier.

2:50pm: How does Sandy compare to other recent massive storms?

2:46pm: The death toll is rising and is now at 13: Local officials in New York, New Jersey, Maryland, Pennsylvania, West Virginia and North Carolina reported 12 dead from the massive storm system, and Toronto police said a Canadian woman was killed by flying debris.

2:37pm: A Twitter account which appears to be run by US power company Con Edison is saying the Reuters report about workers being trapped in a Con Ed power plant is false. The account is @ConEdison.

2:22pm: Reuters is now reporting that the Nine Mile One nuclear reactor in upstate New York has been shut down. It was not clear if the outage was related to Superstorm Sandy.

High winds and flooding hit hundreds of kilometres of Atlantic coastline while heavy snows were forecast farther inland as the centre of the storm marched westward.

The storm's wind field stretched from the Canadian border to South Carolina, and from West Virginia to a point in the Atlantic Ocean about halfway between the United States and Bermuda, easily one of the largest ever seen.

More than 3 million customers were already without power by early evening and more than 1 million people were subject to evacuation orders. Many communities have been swamped by flood waters.

1:55pm: The ABC's Michael Maher is on the banks of the Hudson River in Manhattan.

"I'm watching the water just progressively come further up the street towards me. I'm about five feet away from lapping water at the moment.

"I'd say it's probably about three feet [deep] a little further in front of me.

"It's certainly quite a frightening sight. This is the route that I walk every morning to go for a run along the Hudson and I've never seen it like this before. I've been standing here for about half an hour and in that time the water has come up this street into the centre of Manhattan by about 10 feet. So it is gradually coming into the centre of the island."

More than a million people are now confirmed to be without power in the state of New York alone.

1:45pm: The storm is now weakening as it heads inland. Also, it now appears that earlier reports of the New York Stock Exchange trading floor being flooded are actually untrue.

1:42pm: 19 workers are trapped after an explosion at a Consolidated Edison power station on the east side of Manhattan, Reuters reports.

1:01pm: BREAKING: Bloomberg says the worst of the weather has now passed New York and winds should be below gale force within the next few hours. He says the worst of the storm surge will soon be over.

12:57pm: BREAKING: Mayor Bloomberg is talking now: "an extraordinary" amount of water in lower Manhattan; widespread power outages; patients being evacuated from NY University Hospital after power failures; large amounts of fires caused by electrical faults. He says the 911 system is receiving 10,000 calls per half-hour. More to come.

12:56pm: We're standing by for a live press conference from New York mayor Michael Bloomberg.

12:51pm: JUST IN: US emergency officials have issued a warning for residents around Long Island Sound.

Officials say the worst of the high tide and storm surge is expected to hit in the next hour or so and people are being told to get to higher ground if they still can.

Those who are now trapped in their homes are advised to stay where they are.

"Stay away from windows. Ride this thing out. Do not try to walk through it, do not try and swim through it," an official said.

"If your house is surrounded by water right now, move to a higher level of the house."

12:49am: BREAKING: AFP is reporting that two people have been killed after a tree fell onto their car in New Jersey, according to an emergency management official.

12:15pm: This dramatic video just in: Watch the moment a giant crane buckled as high winds hit New York City earlier today. The crane was erected on a 306-metre skyscraper under construction near Times Square. Warning: contains strong language.

12:08pm: It's now clear that the Hudson and East rivers have burst their banks in New York, causing widespread flooding in lower Manhattan. There are also reports of hundreds of guests being evacuated from a hotel near the site of the crane collapse.

11:35am: BREAKING: The Wall Street Journal says at least five people have been killed in storm-related incidents in New York.

Social media is alive with pictures showing what users say is the flooding in lower New York City; the photos show cars floating in the streets. High tide is expected within 20 minutes.

11:16am: New York's Fire Department says a man has been killed after a tree fell on his house in Queens.

11:09am: There are reports of widespread blackouts in New York City. This from the New York Times:

"Around 7pm the torch at the top of the Statue of Liberty, which shone all through thick daytime fog, driving rain and an early nightfall, went black.

"Soon after, lights began blinking out in buildings all over Lower Manhattan, and two flashes that looked like explosions lighted the sky above New Jersey."

11:06am: BREAKING: The US National Hurricane Centre says former hurricane Sandy has made landfall along the New Jersey coast.

11:00am: Residents outside New York City say they have been told they are "on their own" until daylight.

Linda Floyd told ABC News 24 her family was riding it out at home in the town of Maplewood in New Jersey.

"It's very dark. Winds here are shaking the homes. There are many trees down all throughout our town. Most of our town is without power," she said.

"I have a very handy Australian husband so we have a generator hooked up."

Ms Floyd says Mapletown is a commuter town about 18 miles from New York City.

"Were right in the think of the storm at the moment. There are trees down everywhere that are causing damage to homes, to garages, to powerlines," she said.

"There is a river running through our town that will flood."

She says officials have told residents "they are on their own until daylight".

10:57am: The New York Times is reporting that cars are floating in floodwaters on Wall Street in lower Manhattan.

"As the evening high tide was drawing closer, there were reports of flooding in several low-lying areas around the five boroughs, places that had not in recent memory experienced flooding," the Times blog reports.

10:56am: DFAT has updated its travel warning telling Australians to monitor media in the US and adhere to all warnings from officials.

The New York Fire Department says there are no injuries or people trapped at the site of the 8th Avenue Manhattan apartment building collapse.

10:31am: Atlantic City's public safety director says "most of the city is underwater" and parts of the city's famous boardwalk are breaking up.

Emily Previti from the Atlantic City Press Office described the scene from Atlantic City:

"It's frightening to be outside. The weather is something that most people here have never felt or seen before," she said.

"Individual property owners who are trying to hunker down... I can only imagine they're feeling very frantic."

10:21am: BREAKING: Atlantic City's public safety director says "most of the city is underwater".

On the latest weather report on ABC News24: Hurricane Sandy has now been downgraded to a "post-tropical cyclone".

10:16am: BREAKING: Wall Street is now without power.

Kristi Maroc, an Australian in New York, is at the scene of the four-storey building collapse in Manhattan:

"The front of building's gone. It looks like a doll's house, like if you've move the front off the building you can see straight into the apartment," she said.

"I'm on 8th Avenue. I'm just standing in the doorway of the building. At the moment haven't seen any ambulances. There's cranes holding up the front of the building. There's pieces of the building falling off."

9:00am: The state of emergency currently extends across nine states. They are: Connecticut; Delaware; Maryland; New Jersey; New York; Pennsylvania; Rhode Island; Virginia; West Virginia.

8:47am: New York Mayor Michael Bloomberg has just given a press conference.

He told New Yorkers that the worst of the storm was about to hit the city and said the time for evacuation had now passed.

"As everybody knows we're already seeing significant impacts from the storm and the worst of it is about to hit. I think we have done all we can to prepare.

"Now as the storm intensifies the most important thing I can say is if you're in your home or somewhere safe where you can remain, stay there. The time for relocation or evacuation is over. Conditions outside are dangerous and they're only going to get worse in the hours ahead."